What immediately comes to mind when many of us think of an atoll is a
desolate, circular array of coral reefs with white, sandy islands
populated by a few lonely, swaying palm trees and perhaps a castaway or
two. Were we to consider them more closely, however, we would find that
this standard perception just skims the surface. Atolls are, in fact,
some of the most complex and vibrant structures on the planet. Built
diligently over thousands of years by tiny, sea anenome-like coral
polyps, these ring shaped coral structures can be tens of kilometers in
diameter with individual reefs large enough to support lush tropical
islands and even small cities. As is the case with any living coral
structure, countless species of fish and invertebrates can be found
inhabiting the waters in and around an atoll. But unlike the fringing
reefs along Floridas coast or even the barrier reefs off the shore
of Australia, atolls do not border anything. Instead, they sit on a
coral base that often rises thousands of meters from the oceans
floor in some of the most remote areas of the tropical oceans.

Though scientists have been studying atolls at least since the time
of Charles Darwin in the mid-1800s, many mysteries remain about exactly
how they form and what factors determine their shape. One such question
centers on the degree to which climate conditions affect the growth of
the coral reefs that make up an atoll. Some researchers believe that
the weather acts primarily to erode and diminish the underlying
structure of fully formed reefs. Others believe that given the right
conditions, waves and currents shape the reefs by actually stimulating
growth. Resolving this debate one way or the other hasnt been easy
though, as most atolls are in remote areas of the ocean and are hard to
get to, let alone map or fully analyze.

In many ways, the Maldives are the archetype
of the sunny coral atoll. (Photograph Copyright Ismail Faiz)

The classic
atoll is composed of a coral reef encircling a shallow lagoon, like this ring-shaped reef (or "faro") in the Maldives. (Photograph
courtesy Abdulla Naseer, Dalhousie University)

Two scientists at Dalhousie University in Halifax, Nova Scotia, may
now be on their way to solving this riddle of the atolls. Using
satellite imagery collected by Landsat 7, marine ecologist Bruce Hatcher
and Maldivian doctoral student Abdulla Naseer are mapping out the reefs
of the atoll archipelago that make up the Maldives in the Indian Ocean.
By comparing the maps to wind and wave data from the region, they are
attempting to discern if the monsoons that blow regularly from the east
and the west played a role in shaping the Maldives. And they believe
such knowledge may have a practical application as well. Understanding
how the coral reefs grow could help the Maldives people shield
themselves from the rising sea levels that may occur as a result of
global warming.